The present invention relates to ophthalmoscopic viewing systems for use with a slit lamp or other biomicroscope for diagnosis and/or treatment of structures within the eye, including, for example, the fundus, the anterior chamber angle, iris and ciliary process. In particular, the invention relates to ophthalmoscopic viewing systems for creating a real image outside the eye of structures within the eye.
Special ophthalmoscopic lenses have been developed for viewing structures within the eye for purposes of diagnosis and/or other surgical treatment of the eye. For example, indirect ophthalmoscopic lenses are known which produce a real image of a patient's fundus outside of the eye for use with a slit lamp or other biomicroscope. Direct ophthalmoscopic lenses are also known which produce a virtual image within the eye of the patient's fundus which can be viewed by the physician. Generally speaking, the virtual image produced by a direct ophthalmoscopic lens has a higher magnification than the real image produced by an indirect ophthalmoscopy lens, but has a smaller field of view. The virtual image produced by an direct ophthalmoscopic lens is a true, upright image. The real image produced by an indirect ophthalmoscopic lens is inverted and reversed, so that either the physician must learn to work with the inverted and reversed image or special measures must be taken to convert the initial real image produced by the indirect ophthalmoscopic lens to a true, upright image such as disclosed, for example, in U.S. Pat. No. 4,721,378 to David Volk. With the use of such additional measures, it is possible to employ an indirect ophthalmoscopic lens to observe a large field of view of a true and upright image of a patient's fundus.
Gonioscopic devices are available for viewing the anterior chamber angle of a patient's eye. Known devices, such as the Koeppe lens, employ a contact lens having a highly curved convex anterior lens surface. The contact lens, together with a tear layer between the cornea and the posterior surface of the contact lens, shifts the cornea-air interface to the highly curved anterior lens surface. Due to the more nearly normal (or perpendicular) light passage through the anterior surface, light rays originating at the anterior chamber angle pass through the front surface of the cornea, into the lens and out of the steeply curved anterior surface. Although the Koeppe lens produces a true and upright magnified image of the anterior chamber angle, the field of view is small and the physician is required to view the image at a highly off-axis position.
Mirrored gonioscopic lenses are known, such as the Goldmann lens, which employ an angulated mirror within the lens. The lens operates to eliminate the power of the cornea to avoid total reflection of the light rays at the cornea-air interface. Light rays from the anterior chamber angle enter the lens and are reflected by the mirror along the line of vision of the viewer. However, because of the mirror, the image of the angle is reversed and inverted. Additionally, like the Koeppe lens, the field of view is very small.
It would be desirable to have an ophthalmoscopic viewing system for viewing structures within the eye, including anterior structures such as the anterior chamber angle, iris and ciliary process, which has advantageous features of an indirect ophthalmoscopy lens, including the provision of a large field of view, so that the physician could observe an uninterrupted 360.degree. annular ring of the iris and anterior chamber angle, and preferably view such an image in an upright and correctly oriented position.
It would further be desirable to provide for improved ophthalmoscopic viewing systems for producing a true and upright real image outside of the eye of structures within the eye, including the fundus, to facilitate diagnosis and treatment.